Catalyzed synthesis of crystalline linear polymer nanofibers

ABSTRACT

Crystalline nanofibers of linear polyethylene with an ultrahigh molecular weight (6,200,000) and a diameter of 30 to 50 nanometers were formed by the polymerization of ethylene with mesoporous silica fiber-supported titanocene, with methylalumoxane as a cocatalyst. Small-angle x-ray scattering analysis indicated that the polyethylene fibers consist predominantly of extended-chain crystals. This observation indicates a potential utility of the honeycomb-like porous framework as an extruder for nanofabrication of polymeric materials.

RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 60/203,328 filed May 11, 2000.

FIELD OF THE INVENTION

[0002] The present invention relates generally to a method of manufacturing a linear polymer and the resulting linear polymer, and a catalyst support for use in preparing a polymer from a monomer. The present invention relates more specifically to a method of manufacturing crystalline nanofibers of linear polyethylene with an ultrahigh molecular weight (6,200,000) and a diameter of 30 to 50 nanometers.

BACKGROUND OF THE INVENTION

[0003] Recent developments in polymerization catalysis have enabled the precise control of the primary properties of polymers such as molecular weight, co-monomer sequence, and stereo sequence (see 0. W. Webster, Science 251, 887 (1991); Y. Okamoto and T. Nakano, Chem. Rev. 94, 349 (1994); S. Kobayashi, Ed., Catalysis in Precision Polymerization (Wiley. New York, 1997)). However, for polymers to be used as commodity materials, molecular orientation (crystal structure) (P. Smith and P. J. Lemstra, J. Mater. Sci. 15, 505 (1980); J. C. M. Torfs and A. J. Pennings, J. Appl. Polym. Sci. 26, 303 (1981); J. H. Lee, R. M. Brown Jr., S. Kuga, S. Shoda, S. Kobayashi, Proc. Natl. Acad. Sci, U.S.A. 91, 7425 (1994)) or morphology (E. Evans, H. Bowman, A. Leung, D. Needham, D. Tirrel, Science 273, 933 (1996); S. B. Roscoe, J. M. Frechet, J. F. Walzer. A. J. Dias, ibid 280, 271 (1998); K. Akagi et al., ibid 282, 1683 (1998), D. A. Tomalia, Adv. Mater. 6, 529 (1994); D.-L. Jiang and T. Aida, Nature 388, 454 (1997); M. Fisher and F. Vogtle, Angew. Chem. Int. Ed 38, 884 (1999)), or both, must also be controlled. Postprocessing steps, such as extrusion or spinning, are usually required to fabricate polymeric materials that perform more elaborate functions. Some crystalline polymers with controlled morphology are already produced in nature. For example, in the biosynthesis of highly crystalline cellulose fibers by the bacterium Acetobacter xylinum, cellulose synthase in a cellular membrane forms fine elementary fibrils of cellulose. They are then assembled into macrofibrils and fibers by extrusion through nanopores arranged in the cellular membrane (T. P. Nevell, Ed., Cellulose Chemistry and Its Applications (Halsted, New York, 1985), chap. 2.). A regular arrangement of multiple catalytic sites on mesostructured porous materials could mimic this natural system and produce crystalline polymers with a fibrous morphology (FIG. 1).

SUMMARY OF THE INVENTION

[0004] An object of the present invention is to provide a highly crystalline polymer fiber.

[0005] Another object of the present invention is to provide an oriented, extended-chain linear polymer.

[0006] Further, an object of the present invention is to provide a method of manufacturing a highly crystalline polymer fiber and/or an oriented, extended-chain linear polymer.

[0007] More, an object of the present invention is to provide a catalyst support for use in preparing the above-mentioned polymer from a monomer.

[0008] The present inventors have found that the following inventions <1>to <39>can achieve the above-mentioned object(s):

[0009] <1>A method of manufacturing a linear polymer comprising the steps of:

[0010] preparing a tubular catalyst support carrying a catalyst; and

[0011] polymerizing a monomer in the presence of the tubular catalyst support, to obtain a linear polymer.

[0012] <2>In the above-mentioned method <1>, the step of polymerizing is conducted in the presence of a plurality of the tubular catalyst supports.

[0013] <3>In the above-mentioned method <1>, the step of polymerizing is conducted in the presence of a plurality of the tubular catalyst supports which are adjacent to each other.

[0014] <4>In the above-mentioned method <1>, the step of polymerizing is conducted in the presence of a plurality of the tubular catalyst supports which are adjacent to each other, each of tubular catalyst supports has a substantially hexagonal cross-section in a direction orthogonal to a longitudinal direction of the support, and the plurality of the tubular catalyst supports are disposed in a honeycomb-like arrangement as viewed in a direction orthogonal to a longitudinal direction of the supports. <5>In the above-mentioned methods <1>to <4>, the linear polymer is an oriented linear polymer. <6>In the above-mentioned methods <1>to <5>, the tubular catalyst support comprises silica, and the silica carries the catalyst. <7>In the above-mentioned methods <1>to <6>, the catalyst is a titanium catalyst. <8>In the above-mentioned methods <1>to <7>, the catalyst comprises TiX₂, wherein X represents cyclopentadienyl, derivatives of cyclopentadienyl, and analogs of cyclopentadienyl. <9>In the above-mentioned method <8>, X is selected from the group consisting of cyclopentadienyl, pentamethylcyclopentadienyl, dimethylsilyl-bis-cyclopentadienyl, indenyl, and ethylene-bis-indenyl. <10>In the above-mentioned method <8>, X is cyclopentadienyl. <11>In the above-mentioned methods <1>to <10>, an opening of the tubular catalyst support has a diameter of from 1 to 10 nm, preferably from 2 to 5 nm, and more preferably from 2 to 3 nm.

[0015] <12>In the above-mentioned methods <1>to <11>, the tubular catalyst support is made of zeolite.

[0016] <13>In the above-mentioned methods <1>to <12>, the monomer is ethylene, and the linear polymer is polyethylene.

[0017] <14>In the above-mentioned methods <1>to <13>, a co-catalyst, which is selected from the group consisting of alkylalumoxanes and trialkylaluminums, is used in the step of polymerizing the monomer.

[0018] <15>In the above-mentioned method <14>, the co-catalyst is methyl-alumoxane.

[0019] <16>In the above-mentioned method <14>or <15>, a ratio Al/Ti (molar ratio) of aluminum contained in the co-catalyst to titanium contained in the titanium catalyst ranges from 10 to 10,000, preferably 50 to 5,000, and more preferably 500 to 2,000.

[0020] <17>In the above-mentioned methods <1>to <16>, the linear polymer has a microfiber structure having a diameter of from 10 to 150 nm, preferably from 20 to 100 nm, and more preferably from 40 to 80 nm.

[0021] <18>In the above-mentioned methods <1>to <16>, the linear polymer is crystalline linear polyethylene, and the polyethylene has a diameter of from 10 to 150 nm, preferably from 20 to 100 nm, and more preferably from 40 to 80 nm.

[0022] <19>In the above-mentioned methods <1>to <18>, the monomer is ethylene, and the step of polymerizing the ethylene monomer is conducted at a temperature of from 10 to 50° C. and preferably 20° C., and at a pressure of from 1 to 20 atm and preferably 10 atm.

[0023] <20>A linear polymer obtained from the method according to any one of the above-mentioned methods <1>to <19>.

[0024] <21>An oriented linear polymer.

[0025] <22>In the above-mentioned polymer <21>, the polymer has a degree of crystallinity of 90% or more.

[0026] <23>In the above-mentioned polymer <21>or <22>, the polymer has a microfiber structure having a diameter of from 10 to 150 nm, preferably from 20 to 100 nm, and more preferably from 40 to 80 nm.

[0027] <24>In the above-mentioned polymers <21>to <23>, the polymer is free from small-angle X-ray scattering (SAXS) signals at 0.324 degrees (2θ) as measured by SAXS.

[0028] <25>An oriented, extended-chain linear polymer.

[0029] <26>In the above-mentioned polymer <25>, the polymer has a degree of crystallinity of 90% or more.

[0030] <27>In the above-mentioned polymer <25>or <26>, the polymer has a microfiber structure having a diameter of from 10 to 150 nm, preferably from 20 to 100 nm, and more preferably from 40 to 80 nm.

[0031] <28>In the above-mentioned polymers <25>to <27>, the polymer is free from small-angle X-ray scattering (SAXS) signals at 0.324 degrees (2θ) as measured by SAXS.

[0032] <29>A catalyst support for use in preparing a polymer from a monomer, comprising a tubular catalyst support carrying a catalyst.

[0033] <30>The above-mentioned catalyst support <29>may comprise a plurality of tubular catalyst supports which are adjacent to each other.

[0034] <31>The above-mentioned catalyst support <29>may comprise a plurality of tubular catalyst supports which are adjacent to each other, each of tubular catalyst supports has a substantially hexagonal cross-section in a direction orthogonal to a longitudinal direction of the support, and the plurality of the tubular catalyst supports are disposed in a honeycomb-like arrangement as viewed in a direction orthogonal to a longitudinal direction of the supports.

[0035] <32>In any one of the above-mentioned catalyst supports <29>to <31>, the tubular catalyst support comprises silica, and the silica carries the catalyst.

[0036] <33>In any one of the above-mentioned catalyst supports <29>to <32>, the catalyst is a titanium catalyst.

[0037] <34>In any one of the above-mentioned catalyst supports <29>to <33>, the catalyst comprises TiX₂, wherein X represents cyclopentadienyl, derivatives of cyclopentadienyl, and analogs of cyclopentadienyl.

[0038] <35>In the above-mentioned catalyst support <34>, X is selected from the group consisting of cyclopentadienyl, pentamethylcyclopentadienyl, dimethylsilyl-bis-cyclopentadienyl, indenyl, and ethylene-bis-indenyl.

[0039] <36>In the above-mentioned catalyst support <34>, X is cyclopentadienyl.

[0040] <37>In any one of the above-mentioned catalyst supports <29>to <36>, an opening of the tubular catalyst support has a diameter of from 1 to 10 nm, preferably 2 to 5 nm, and more preferably 2 to 3 nm.

[0041] <38>In any one of the above-mentioned catalyst supports <29>to <37>, the tubular catalyst support is made of zeolite.

[0042] <39>In any one of the above-mentioned catalyst supports <29>to <38>, the support is for use in preparing polyethylene from ethylene.

BRIEF DESCRIPTION OF THE DRAWINGS

[0043]FIG. 1 shows conceptual scheme for the growth of crystalline fibers of polyethylene by mesoporous silica-assisted extrusion polymerization.

[0044]FIG. 2 shows polymerization of ethylene (10 atm) in toluene at 20° C.

[0045]FIGS. 3A to 3C show SEM images of freeze-dried polyethylene at three different magnifications.

[0046]FIG. 4A shows XRD pattern (indexed peaks: assigned to orthorhombic phase).

[0047]FIG. 4B shows SAXS pattern of polyethylene fibers freezed-dried from benzene.

[0048]FIG. 4C shows a typical SAXS pattern of a commercial, high-density crystalline polyethylene, for comparison.

[0049]FIG. 5 shows DSC melting curve of polyethylene fibers freezed-dried from benzene.

[0050]FIGS. 6A and 6B shows SEM images of a piece of Cp₂Ti-MSF, treated with a toluene solution of MAO (Al/Ti=1,000), dried under reduced pressure, and then exposed to ethylene (10 atm), at two different magnification.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0051] The present invention will be described in detail, hereinafter.

[0052] The present invention provides a method of manufacturing a linear polymer. The method comprises a step of preparing a tubular catalyst support carrying a catalyst; and a step of polymerizing a monomer in the presence of said tubular catalyst support, to obtain a linear polymer.

[0053] In the method of the present invention, the polymerization step may be conducted in the presence of a plurality of the tubular catalyst supports. Preferably, the tubular catalyst supports may be adjacent to each other. Each of tubular catalyst supports may have a substantially hexagonal cross-section in a direction orthogonal to a longitudinal direction of the support. The plurality of the tubular catalyst supports may be disposed in a honeycomb-like arrangement as viewed in a direction orthogonal to a longitudinal direction of the supports.

[0054] Further, the tubular catalyst support may comprise silica, and the silica may carry the catalyst. The catalyst may be a titanium catalyst. For example, the catalyst may comprise TiX₂, wherein X represents cyclopentadienyl, derivatives of cyclopentadienyl, and analogs of cyclopentadienyl. Preferably, X may be selected from the group consisting of cyclopentadienyl, pentamethylcyclopentadienyl, dimethylsilyl-bis-cyclopentadienyl, indenyl, and ethylene-bis-indenyl. More preferably, X may be cyclopentadienyl.

[0055] The tubular catalyst support used in the method of the present invention may have an opening having a diameter of from 1 to 10 nm, preferably from 2 to 5 nm, and more preferably from 2 to 3 nm. The tubular catalyst support may be made of zeolite.

[0056] In the polymerization step of the present invention, monomer used may be ethylene, and a linear polymer obtained may be polyethylene. If the monomer is ethylene, the step of polymerizing the ethylene monomer may be conducted at a temperature of from 10 to 50° C. and preferably 20° C., and at a pressure of from 1 to 20 atm and preferably 10 atm.

[0057] In the polymerization step, a co-catalyst may be used. The co-catalyst may be at least one selected from the group consisting of alkylalumoxanes and trialkylaluminums. Preferably, the co-catalyst is methyl-alumoxane. If the co-catalyst is used in the polymerization step, a ratio Al/Ti (molar ratio) of aluminum contained in the co-catalyst to titanium contained in the titanium catalyst ranges from 10 to 10,000, preferably 50 to 5,000, and more preferably 500 to 2,000.

[0058] Further, the present invention provides a linear polymer, an oriented linear polymer, and/or an oriented, extended-chain linear polymer. The linear polymer, an oriented linear polymer, and/or an oriented, extended-chain linear polymer may be obtained by the above-mentioned method.

[0059] The linear polymer, an oriented linear polymer, and/or an oriented, extended-chain linear polymer of the present invention may have a microfiber structure having a diameter of from 10 to 150 nm, preferably from 20 to 100 nm, and more preferably from 40 to 80 nm. Preferably, the linear polymer may be crystalline linear polyethylene, and the polyethylene may have a diameter of from 10 to 150 nm, preferably from 20 to 100 nm, and more preferably from 40 to 80 nm.

[0060] Further, the polymer of the present invention may have a degree of crystallinity of 90% or more. The polymer may be free from small-angle X-ray scattering (SAXS) signals at 0.324 degrees (2θ) as measured by SAXS.

[0061] The present invention further provides a catalyst support for use in preparing a polymer from a monomer, as mentioned above. The catalyst support may comprise a tubular catalyst support carrying a catalyst. The catalyst support may comprise a plurality of tubular catalyst supports which are adjacent to each other. Further, the catalyst support may comprise a plurality of tubular catalyst supports which are adjacent to each other, each of tubular catalyst supports may have a substantially hexagonal cross-section in a direction orthogonal to a longitudinal direction of the support, and the plurality of the tubular catalyst supports may be disposed in a honeycomb-like arrangement as viewed in a direction orthogonal to a longitudinal direction of the supports. The catalyst support may comprise silica, and the silica may carry the catalyst. The catalyst may be a titanium catalyst, as mentioned above.

[0062] In more detail, the present invention provides the production of crystalline polyethylene fibers with a diameter of 30 to 50 nm by the polymerization of ethylene with titanocene (Cp₂Ti, where Cp is the cyclopentadienyl ligand) supported by a fibrous mesoporous silica in conjunction with methyl-alumoxane (MAO) as a cocatalyst. Mesoporous silica has a honeycomb-like framework with a uniform, controllable pore diameter from 15 to 100 Å (see J. S. Beck et al., J. Am. Chem. Soc. 114, 10834 (1992); A. Corma, Chem. Rev. 97, 2373 (1997)). It is made up of a hexagonal arrangement of the linear channels. Recently, a new class of mesoporous materials called mesoporous silica fiber (MSF) has been developed, consisting of uniformly sized mesoporous (27 Å) arranged in a parallel direction to the fiber axis (see G. D. Stucky et al., Adv. Mater. 9, 974 (1997)). A sol-gel process at a water-oil interface can easily prepare this material. We used this material as a solid support of titanocene for the polymerization of ethylene (For examples of polymerization with mesoporous materials, see C.-G. Wu and T. Bein, Science 266, 1013 (1994); S. M. Ng, S. Ogino, T. Aida, K. A. Koyano, T. Tatsumi, Macromol. Rapid Commun. 18, 991; (1997); K. Kageyama, S. Ogino, T. Aida, T. Tatsumi, Macromolecules 31, 4069 (1998); and for examples of olefin polymerization with mesoporous materials, see Y.-S. Ko, T.-K. Han, J.-W. Park, S.-I. Woo. Macromol. Rapid Commun. 17, 749 (1996); J. Tudor and D. O'Hare, Chem. Commun. 1997, 603 (1997); L. K. M. van Looveren et al., Angew. Chem Int. Ed 37, 517 (1998)).

EXAMPLES

[0063] The present invention will be demonstrated by way of the following examples, but is in no way limited by these examples.

[0064] Example 1

[0065] The MSF-supported titanocene (Cp₂Ti-MSF) was prepared according to a modified method of Thomas and co-workers. That is, MSF (0.3 g) was treated with a dichloromethane solution of titanocene dichloride (Cp₂TiCl₂) at 20° C. in the presence of triethylamine as a proton scavenger. After stirring for 18 hours, an insoluble material was isolated by filtration and washed repeatedly with dichloromethane. The amount of Cp₂Ti mounted on the MSF surface was 6×10⁻⁵ mol Ti g⁻¹ (Si/Ti=280), as determined by inductively coupled plasma mass spectrometry (ICP-MS) (see T. Maschmeyer, F. Rey, G. Sankar, J. M. Thomas. Nature 378, 159 (1995)). The powder x-ray diffraction (XRD) pattern of Cp₂Ti-MSF showed peaks characteristic of a hexagonal symmetry with a d spacing of 3.8 nm (wall thickness+pore diameter). Similar to the case for MSF (see G. D. Stucky et al., Adv. Mater 9, 974 (1997)), transmission electron microscopy (TEM) of finely ground Cp₂Ti-MSF showed a clear image of regularly arranged macroscopic pores with a diameter of 2 to 3 nm.

[0066] The polymerization of ethylene with Cp₂Ti-MSF in the presence of MAO gave a cocoon-like solid mass consisting of fibrous polyethylene (PE). For example, a toluene (20 ml) solution of MAO (Al/Ti=1000) was added under N₂ to a stainless steel autoclave (100 ml) containing dried Cp₂Ti-MSF (50 mg; 3×10⁻⁶ mol Ti) and a stirring bar in a glass cylinder (diameter=2.5 cm), and the mixture was stirred for 1 hour at 20° C. The resulting suspension was pressurized by the introduction of ethylene and stirred magnetically under a constant pressure (10 atm) at 20° C. After 4 hours, the autoclave was opened, and the resulting cocoon-like polymeric mass, which absorbed most of the solvent (FIG. 2A), was picked out with tweezers (FIG. 2B) and dipped in a large volume of benzene. After stirring for 48 hours, the polymeric mass was freeze-dried to give 1.8 g of colorless PE. Here, the production rate of PE was estimated to be 15 kg mol⁻¹ hour⁻¹ bar⁻¹. Quite unexpectedly, the PE thus obtained had an ultrahigh viscometric molecular weight (M_(v)=6,200,000) and a higher density (1.01 g cm⁻³) than that of a PE obtained with a homogeneous system, Cp₂TiCl₂-MAO, under similar conditions (0.97 g cm⁻³) (measured using a flotation method with methanol/dioxane at 30° C.). The ¹³C nuclear magnetic resonance (NMR) spectrum of the PE in 1,2,4-trichlorobenzene-C₆D₆ at 130° C. showed a single CH₂ signal at δ30.1 ppm (see G. B. Galland, R. F. de Souza, R. S. Mauler, F. F. Nunes, Macromolecules 32, 1620 (1999)), which indicates a linear sequence of the repeating ethylene units without any branch structures.

[0067] Scanning electron microscope (SEM) images of the freeze-dried PE reveal bundles of PE fibers (FIG. 3, A and B). When the view was further magnified (field emission SEM), ultra-thin discrete fibers with a smooth surface, 30 to 50 nm in diameter, were observed (FIG. 3C). Polarization microscopy of the PE fibers showed a clear birefringence in the fraying edge region, which suggests that the fibers are crystalline. The XRD pattern (FIG. 4A) was typical of crystalline PEs having [110] and [200] diffraction peaks at 21.6° and 23.8°, respectively (see S. Krimm and A. V. Tobolsky, J. Polym. Sci. 7, 57 (1951)), whereas an amorphous halo, which should be observable around 19.6°, was negligibly small. The XRD pattern also showed several other diffraction peaks at 15.3°, 17.4°, 23.0°, 26.7°, 27.4°, and 27.7° that have not been observed for ordinary crystalline PEs. Small-angle x-ray scattering (SAXS) of the crystalline PE fibers (FIG. 4B) showed only a diffuse scattering without any diffraction peaks due to folded-chain crystals (see B. G. Ranby, F. F. Morehead, N. M. Walter, ibid 44, 349 (1960); L. Mandelkern, A. S. Posner, A. F. Diorio, D. E. Roberts, J. Appl. Phys. 32, 509 (1961)), in contrast with the pattern of a commercial, high-density crystalline PE (FIG. 4C). Thus, the PE fibers consist predominantly of extended-chain crystals. Thermal analysis of the PE fibers by differential scanning calorimetry (DSC; FIG. 5) under unconstrained conditions showed a main endotherm at 140° C. with a broad peak centered at a much higher temperature (159° C.), where the heat of fusion (AH) was evaluated to be 350 J g⁻¹. The PE prepared with the homogeneous Cp₂TiCl₂-MAO system showed a single endotherm at a lower temperature (130° C.) with a much smaller ΔH of 207 J g⁻¹. Taking into account the result of SAXS, the broad endotherm centered at 159° C. (FIG. 5) is attributable to the phase transition of the extended-chain crystals from an orthorhombic phase to a hexagonal phase and the melting of the hexagonal phase (see A. J. Pennings and A. Zwijnenburg, J. Polym Sci. Polym. Phys. Ed. 17, 1011 (1979)). In the second stage of heating, such a high-temperature endotherm was no longer observed, whereas only a single peak (T_(m)) was observed at a lower temperature (130° C.). Furthermore, the several distinctive XRD peaks observed in FIG. 4A also disappeared when the PE fibers were melted.

[0068] From these observations, it is evident that each PE fiber consists of extended-chain crystals, but the fibers are not regularly oriented, leading to the formation of a porous cocoon-like assembly with a large surface area. Thus, the extraordinary peaks in the XRD pattern (FIG. 4A) may be attributed to specific diffractions of the PE crystals in the surface domain of the fiber, which must be different from those of the orthorhombic crystalline phase in the inner domain.

[0069] For the formation of the crystalline PE fibers with the MSF-supported titanocene (Cp₂Ti-MSF), we postulate an “extrusion polymerization” mechanism (FIG. 1) similar to the biosynthesis of crystalline cellulose. Polymer chains, formed at the activated titanocene sites within the individual mesopores, are extruded into the solvent phase and assembled to form extended-chain crystalline fibers. As the pore diameter of the MSF (27 Å) is much smaller than the lamellar length of ordinary PE crystals (˜100 Å) (see W. D. Niegisch and P. R Swan, J. AppL. Phys. 31, 1906 (1960)), the PE chains are likely prevented from folding within the mesopores. To lend support to the extrusion polymerization mechanism, we evaporated a reaction mixture of Cp₂Ti-MSF with MAO in toluene to dryness and exposed the residue to ethylene. The SEM images of the polymerization mixture (FIG. 6) indicated the formation of PE only on the circular cross sections of the silica fibers where the pore exits are opened.

[0070] Comparative Example 1

[0071] A nonfibrous mesoporous silica, MCM-41 (see J. S. Beck et al., J. Am. Chem. Soc. 114, 10834 (1992); A. Corma, Chem. Rev. 97, 2373 (1997)) was used in place of MSF as the solid support of titanocene. MCM-41 was prepared by a method similar to that for the preparation of Cp₂Ti-MSF A crystalline PE containing a fibrous fraction was obtained by the following conditions: The amounts of Cp₂Ti mounted on MCM-41 and amorphous silica were both 5×10⁻⁵ mol Ti g⁻¹. Polymerization conditions: supported catalyst, 50 mg (2.5×10⁶ mol) Ti; co-catalyst, MAO (Al/Ti=500); ethylene pressure, 10 atm; 20° C., 13.5 hours. PE yields: 1.8 g Cp₂Ti-MCM-41-MAO, 1.0 g Cp₂Ti-amorphous silica-MAO. However, it showed ordinary XRD and DSC patterns (a single endotherm at 142° C.; ΔH=222 J g⁻¹).

[0072] On the other hand, use of an amorphous silica-supported titanocene-MAO system (Prepared by a method similar to that for the preparation of Cp₂Ti-MSF. The amounts of Cp₂Ti mounted on MCM-41 and amorphous silica were both 5×10⁻⁵ mol Ti g⁻¹. Polymerization conditions: supported catalyst, 50 mg (2.5×10⁶ mol) Ti; cocatalyst, MAO (Al/Ti=500); ethylene pressure, 10 atm; 20° C., 13.5 hours. PE yields: 1.8 g Cp₂Ti-MCM-41-MAO, 1.0 g Cp₂Ti-amorphous silica-MAO.) for the polymerization resulted in neither fibrous texture nor extraordinary XRD and DSC profiles of the product (a single endotherm at 140° C; AH=167 J g⁻¹).

[0073] It has been reported that a fibrous PE with a diameter of 0.2 to 0.5 μm, containing a fraction of extended-chain crystals, can be obtained by crystallization of PE from a vigorously stirred xylene solution (see A. J. Pennings, C. J. H. Schouteten, A. M. Kiel, J. Polym. Sci. C 38, 167 (1972)). In contrast, our approach is based on an essentially different conception, namely template-assisted extrusion polymerization. Regularly arranged nanoscopic pores on a honeycomb-like solid surface enable in situ formation of much thinner (30 to 50 μm) PE fibers of extended-chain crystals. The present method, using MSF as a nano-extruder, may be widely applicable to the production of fabricated crystalline polymers. Moreover, the use of mesoporous materials of different architectures as templates for polymerization is expected to provide common polymers with some new bulk properties. 

What is claimed is:
 1. A method of manufacturing a linear polymer comprising the steps of: preparing a tubular catalyst support carrying a catalyst; and polymerizing a monomer in the presence of said tubular catalyst support, to obtain a linear polymer.
 2. The method according to claim 1, wherein the step of polymerizing is conducted in the presence of a plurality of said tubular catalyst supports.
 3. The method according to claim 1, wherein the step of polymerizing is conducted in the presence of a plurality of said tubular catalyst supports which are adjacent to each other.
 4. The method according to claim 1, wherein the step of polymerizing is conducted in the presence of a plurality of said tubular catalyst supports which are adjacent to each other, each of tubular catalyst supports has a substantially hexagonal cross-section in a direction orthogonal to a longitudinal direction of the support, and said plurality of said tubular catalyst supports are disposed in a honeycomb-like arrangement as viewed in a direction orthogonal to a longitudinal direction of the supports.
 5. The method according to claim 1, wherein said linear polymer is an oriented linear polymer.
 6. The method according to claim 1, wherein said tubular catalyst support comprises silica, and said silica carries said catalyst.
 7. The method according to claim, wherein said catalyst is a titanium catalyst.
 8. The method according to claim 1, wherein said catalyst comprises TiX₂, wherein X represents cyclopentadienyl, derivatives of cyclopentadienyl, and analogs of cyclopentadienyl.
 9. The method according to claim 1, wherein an opening of said tubular catalyst support has a diameter of from 1 to 10 nm.
 10. The method according to claim 1, wherein said tubular catalyst support is made of zeolite.
 11. The method according to claim 1, wherein said monomer is ethylene, and said linear polymer is polyethylene.
 12. The method according to claim 1, wherein a co-catalyst, which is selected from the group consisting of alkylalumoxanes and trialkylaluminums, is used in the step of polymerizing the monomer.
 13. The method according to claim 12, wherein a ratio Al/Ti (molar ratio) of aluminum contained in said co-catalyst to titanium contained in said titanium catalyst ranges from 10 to 10,000.
 14. The method according to claim 1, wherein said linear polymer has a microfiber structure having a diameter of from 10 to 150 nm.
 15. The method according to claim 1, wherein said monomer is ethylene, and the step of polymerizing the ethylene monomer is conducted at a temperature of from 10 to 50° C., and at a pressure of from 1 to 20 atm.
 16. An oriented linear polymer.
 17. The polymer according to claim 16, wherein said polymer has a degree of crystallinity of 90% or more.
 18. The polymer according to claim 16, wherein said polymer has a microfiber structure having a diameter of from 10 to 150 nm.
 19. The polymer according to claim 16, wherein said polymer is free from small-angle X-ray scattering (SAXS) signals at 0.324 degrees (2θ) as measured by SAXS.
 20. A catalyst support for use in preparing a polymer from a monomer, comprising a tubular catalyst support carrying a catalyst.
 21. The support according to claim 20, comprising a plurality of tubular catalyst supports which are adjacent to each other.
 22. The support according to claim 20, comprising a plurality of tubular catalyst supports which are adjacent to each other, each of tubular catalyst supports has a substantially hexagonal cross-section in a direction orthogonal to a longitudinal direction of the support, and said plurality of said tubular catalyst supports are disposed in a honeycomb-like arrangement as viewed in a direction orthogonal to a longitudinal direction of the supports.
 23. The support according to claim 20, wherein said tubular catalyst support comprises silica, and said silica carries said catalyst.
 24. The support according to claim 20, wherein said catalyst is a titanium catalyst.
 25. The support according to claim 20, wherein said catalyst comprises TiX₂, wherein X represents cyclopentadienyl, derivatives of cyclopentadienyl, and analogs of cyclopentadienyl.
 26. The support according to claim 25, wherein X is selected from the group consisting of cyclopentadienyl, pentamethylcyclopentadienyl, dimethylsilyl-bis-cyclopentadienyl, indenyl, and ethylene-bis-indenyl.
 27. The support according to claim 20, wherein an opening of said tubular catalyst support has a diameter of from 1 to 10 nm.
 28. The support according to claim 20, wherein said tubular catalyst support is made of zeolite.
 29. The support according to claim 20, wherein said support is for use in preparing polyethylene from ethylene. 